1. Field of the Invention
This invention relates to a time switch for controlling a load at a predetermined time.
2. Description of the Related Art
FIG. 15 illustrates an example of this kind of time switch as related art. This time switch includes a main casing 11 having a front opened end, a printed circuit board 32xe2x80x2 disposed in the main casing 11, and an inner cover plate 12 covering the front opened end of the main casing 11.
The printed circuit board 32xe2x80x2 is equipped with a clock function block 21, a terminal block 22 for connecting a load and a load controlling relay 23. The clock function block 21 includes a liquid display for displaying a current time and/or a set time, and so-called rubber switches as push buttons made of an elastic material which utilizes restoring force of elastic material. The circuit board 32xe2x80x2 is fitted in and fixed to the main casing 11 by screws 13. The main casing 11 is coved by an outer cover (not shown). The inner cover plate 12 is disposed at the front opened end so as to cover the printed circuit board 32xe2x80x2 and fixed to the main casing 11 by tightening screws 14. In this state, the liquid display and the rubber switches of the clock function block 21 are exposed through the opening 12a formed in the inner cover plate 12.
As shown in FIG. 16, the clock function block 21 is electrically connected to the printed circuit board 32xe2x80x2 via a connection terminal 9 provided on the circuit board 32xe2x80x2. FIG. 17 illustrates a perspective exploded view of the clock function block 21. The clock function block 21 includes an inner casing 21a, a main block 21b fitted in the inner casing 21a from the upper side thereof, a power source board block 21c fitted in the inner casing 21a from the rear side thereof. A front and rear covers 21e and 21d are fitted onto the inner casing 21a from the upper and rear sides thereof, respectively, to hold the main block 21b and the power source board block 21c in the inner casing 21a. 
In the meantime, the time switch is operated by electric power supplied from a commercial power source, and is required to maintain the clock function and the time-schedule setting function even if a power failure is occurred. Thus, in order to maintain these functions in case of a power failure, a battery as a back-up power source is mounted to the power source board block 21c. In detail, as shown in FIG. 18, the battery B is attached to a battery fixing board 36xe2x80x2 held by a holding plate 21f. The holding plate 21f has a pair of hooking arms 21g for connecting the power source board block 21c to the inner casing 21a. 
The battery B is soldered to the battery fixing board 36xe2x80x2 having electrical parts, some of which are connected to the terminals 44d provided to the power source board block 21c. 
As mentioned above, the time switch is provided with a battery B as a back-up power source. In many cases, a nickel-cadmium battery or a lithium battery is used as the back-up power source, and is required to be replaced with a new one when the battery is dead. In the aforementioned structure, in order to replace the battery with a new one, it is required to disassemble many parts, and then to detach the battery soldered to the fixing board 36xe2x80x2 therefrom. This requires troublesome works.
Furthermore, in a case where the time switch is to be disposed, the nickel-cadmium battery or the lithium battery mounted therein should be taken out for a separate disposition in order to avoid polluting the environment. However, since troublesome and time-consuming jobs are required to remove the battery, in many cases, the time switch had been disposed without removing the battery.
An object of the present invention is to provide a time switch equipped with a battery as a back-up power source which is securely mounted and can easily be removed when the battery is replaced with a new one and/or when the time switch is scraped.
According to a first aspect of the present invention, a time switch includes a circuit board equipped with a time switch circuit operated by a commercial power source, a battery board to which a back-up battery for supplying a back-up power to the circuit board in case of an interruption of a power supply from the commercial power source is mounted, and a casing in which the circuit board and the battery board are mounted, wherein the battery board is a member separated from the circuit board.
With this time switch, since the battery board is a member separated from the circuit board, a replacement or disposal of the back-up battery can be easily be performed by detaching the battery board from the circuit board.
According to a second aspect of the present invention, a time switch includes a circuit board equipped with a time switch circuit operated by a commercial power source, a battery board to which a back-up battery for supplying a back-up power to the circuit board in case of an interruption of a power supply from the commercial power source is mounted, and a casing in which the circuit board and the battery board are mounted, wherein the battery board is connected to the circuit board by way of an easy-to-break portion having a relatively weak mechanical strength.
With this embodiment, since the battery board is connected to the circuit board by way of an easy-to-break portion, the manufacturing thereof can be easily performed. Furthermore, since the battery board can easily be detached from the circuit board by breaking the easy-to-break portion, a disposal of the back-up battery can easily be performed.
The easy-to-break portion may be a groove formed along a boundary between the battery board and the circuit board such as a groove having a V-shaped cross-sectional shape.
Other objects and advantages of the present invention will become apparent from the description of the preferred embodiments, which may be modified in any manner without departing from the scope and spirit of the present invention.